1. Field of the Invention
The present invention relates generally to methods and devices for the selective occlusion of body lumens. More particularly, the present invention relates to methods and devices for applying high frequency electrical energy to vaso-occlusion elements within the body lumen to enhance fibrogenic occlusion of the body lumen.
The selective occlusion of blood vessels in a patient is a part of many modem therapeutic treatments, including the control of internal bleeding, the occlusion of blood supply to tumors, the isolation of diseased body organs prior to removal, the relief of blood pressure in a region of aneurism, and the like. While such procedures rely generally on the blockage of arteries, the selective occlusion of veins is also useful in procedures such as veiniotomy.
The selective occlusion of blood vessels can be achieved by a variety of specific techniques. One such technique involves mechanically clamping or occluding the target site within the blood vessel. For example, in open surgical and endoscopic procedures, the body vessel can be externally clamped and radiofrequency energy applied. While the external procedures can be very effective, it requires external access to the lumen and is unsuitable for endoluminal techniques.
Mechanical endoluminal techniques for selective vessel occlusion are also in use. Such techniques include the use of detachable balloons, embolic and vaso-occlusion coils, and the like to physically block the vessel lumen. Detachable balloons are typically advanced to the vessel site at the end of a catheter and inflated with a suitable fluid, such as saline, x-ray contrast or a polymerizable resin, and released from the end of the catheter. These detachable balloons, however, are difficult to deliver and may not be suitable for permanent implantation unless they are used with the polymerizable resin. In addition, the catheter or the balloon can rupture or release prematurely during filling, leaking monomer resin into the vasculature.
Embolic or vaso-occlusion coils are typically introduced through a catheter in a stretched linear form, and assume a relaxed, helical shape when released into a vessel. One of the limitations of these coils is that recanalization of the occlusion site can occur when the initial blood clot is broken down by the body""s natural anticoagulant mechanism (i.e., resorption of the clot). In addition, once the embolic coils are released by the introducer catheter, they are no longer under control and they frequently migrate from the point of initial implantation.
To completely arrest the flow of blood in a vessel and to inhibit recanalization, current methods of coil embolization typically require the use of several embolic coils at the target site in the blood vessel. In this xe2x80x9cnesting techniquexe2x80x9d, the embolic coils are deposited within a vessel to create a mechanical xe2x80x9cplugxe2x80x9d. It has been found, however, that the use of several coils does not always prevent recanalization of the blood vessel, particularly in larger, high flow vessels. Moreover, it often takes a relatively long time for the blood vessel to completely occlude. Therefore, the embolic coils may often migrate into a non-target site prior to vessel occlusion, particularly in larger or high flow vessels. Multiple coils are also more expensive than a single coil and they require more time to position within the vessel, thereby further increasing the cost of the procedure and prolonging the patient""s exposure to the fluoroscope.
Of particular interest to the present invention, the use of monopolar and bipolar radiofrequency devices has been proposed for the occlusion of body vessels from a surrounding lumen or body cavity. For example, U.S. Pat. No. 5,403,311 describes control of vessels bleeding into a body lumen using electrosurgical electrodes which puncture the vessel from within a larger lumen enclosing that vessel. Catheters for radiofrequency injury and occlusion of the cystic duct are described in Becker et al. (1989) Radiology 170:561-562 and (1988) Radiology 167:63-68 and Tanigawa et al. (1994) Acta Radiologica 35:626-628. Methods and catheters for electrosurgical endovascular occlusion are described in Brunelle et al. (1980) Radiology 137:239-240; Cragg et al. (1982) Radiology 144:303-308; and Brunelle et al. (1983) Radiology 148:413-415. Such techniques, however, have not generally been useful in large or high flow blood vessels.
For these reasons, it would be desirable to provide improved methods and devices for endoluminal occlusion of body lumens, and particularly of blood vessels, for use in the procedures described above. Such methods and devices should provide effective occlusion of large or relatively high flow body lumens as well as small body lumens. Preferably, the methods and devices will permit the physician to re-access the occlusion site, to correct recanalization and/or to enhance the occlusion of this site to prevent subsequent recanalization of the body lumen.
2. Description of the Background Art
Methods and devices for implanting vaso-occlusive elements, such as coils, in blood vessels and other lumen are described in U.S. Pat. Nos. 5,354,295; 5,350,397; 5,312,415; 5,261,916; 5,250,071; 5,234,437; 5,226,911; 5,217,484; 5,122,136; 5,108,407; `4,994,069; and 3,868,956; and published PCT applications WO 94/11051; WO 94/10936; WO 94/09705; WO 94/06503; and WO 93/06884. Some of the devices described in the above listed patents and published applications suggest passing direct current through the element to enhance blood clotting.
Electrosurgical probes for electrosurgical, electrocautery, and other procedures are described in U.S. Pat. Nos. 5,405,322; 5,385,544; 5,366,490; 5,364,393; 5,281,216; 5,236,410; 4,685,459; 4,655,216; 4,582,057; 4,492,231; 4,209,018; 4,041,952; 4,011,872; 4,005,714; 3,100,489; 2,022,065; 1,995,526; 1,943,543; 1,908,583; and 1,814,791; and published Japanese application 2-121675; published German applications DE 4139029; DT 2646228; and DT 2540968; and published PCT applications WO 95/02366 and WO 93/01758.
A method and system employing RF energy for the direct occlusion of blood vessels and other body lumens are described in co-pending application Ser. No. 08/488,444 filed on Jun. 7, 1995 (attorney docket No. 16807-3), the full disclosure of which is incorporated herein by reference. See also the patent and publications described in the Field of the Invention above.
Methods and apparatus are provided for deploying vaso-occlusive elements into body lumens, such as blood vessels, to occlude a target site within the lumen and for enhancing the occlusion of body lumens that already have vaso-occlusive elements deployed therein. The technique involves applying high frequency electrical energy to an electrically conductive, vaso-occlusive element and generating a thermal reaction at the target site to damage the luminal wall and induce fibrogenic occlusion of the blood vessel around the vaso-occlusive element. The vaso-occlusive element, which is typically an electrically conductive wire coil, helps reduce blood flow within the vessel and provides a larger surface for energy transfer between the electrical energy source and the tissue wall and surrounding blood. The high frequency electrical energy, typically radiofrequency current, is usually sufficient to induce local heating of the luminal wall and also to enhance coagulation of the surrounding blood, thereby initiating clotting. The thermally injured wall then contributes to subsequent fibrosis, thus permanently occluding the lumen.
The vaso-occlusive coil typically has a relatively low electrical resistance so that the high frequency electrical energy flows directly through the vaso-occlusive coil to the luminal wall (i.e., without substantially heating the coil). The electrical energy heats the luminal wall, thereby causing damage and subsequent fibrogenic occlusion of the target site. Alternatively, the vaso-occlusive coil may comprise sufficient electrical resistance such that a portion of the high frequency electrical energy is transferred directly to the coil (rather than the luminal wall) to heat the coil and enhance occlusion around the coil. In this case, the vaso-occlusive coil will preferably have an electrical resistance slightly less than the tissue wall to ensure that the electrical energy flows through at least a substantial portion of the coil.
In one aspect, the method comprises contacting a vaso-occlusive coil that is already deployed at a target site within a body lumen with at least one electrode and applying the high frequency electrical energy to the coil in a monopolar or bipolar fashion. Preferably, the energy is applied in a monopolar mode by contacting the patient""s body with a second, dispersive or return, electrode and then delivering a high frequency current to the first or active electrode, through at least a portion of the vaso-occlusive coil, the surrounding tissue, and finally to the second electrode. For bipolar operation, a separate second electrode may be provided on the catheter, typically spaced proximally from the first electrode so that it will be located within the body lumen. The second electrode will usually be spaced a distance of about 2 mm to 10 cm from the active electrode.
The first electrode will usually be disposed on the distal end of an intravascular catheter. The catheter can be percutaneously introduced via well-known procedures and advanced to the target site in a body lumen in a known manner, typically over a guide wire. The first electrode can be engaged against the vaso-occlusive coil in a variety of ways. For example, the electrode (and optionally a pair of electrodes for bipolar operation) can simply be disposed at a distal location on the catheter which will contact the vaso-occlusive coil when the catheter is advanced through the body lumen to the target site.
Alternatively, the electrode may be provided by a separate member, such as an insulated conventional or specialized guide wire, or a positioner device, which may be insulated by the catheter body. In use, the guideline positioner is extended distal to the catheter body, placed against the vaso-occlusive coil, and the radiofrequency current is applied thereto. In the latter case, a distal portion of the positioner may comprise the active electrode, while the return electrode is located on the catheter or placed externally on the patient.
In other aspects, the method may comprise deploying the vaso-occlusive coil at the target site within the body lumen, adjusting the position of an already deployed vaso-occlusive coil within the target site, or repositioning the coil to another location in the vasculature. For initial deployment, the vaso-occlusive coil will be releasably engaged by the positioner and optionally advanced through the axial lumen of the catheter for deployment. For repositioning, the coil may be captured by the positioner and partially or fully retracted into the axial lumen for adjusting coil placement or repositioning the coil to another location. Typically, the coil will be repositioned when previous attempts to occlude a target site have not completely succeeded and the coil is not fixed at the site. A particular advantage of the present invention is that the coil can be held in place within the body lumen by the positioner until the high frequency voltage or current has been applied thereto. Once the voltage has generated a sufficient thermal reaction to induce spasm and localized edema/narrowing of the vessel (and subsequent fibrogenic occlusion of the lumen) around the coil, the coil will be released from the positioner and the positioner removed from the vasculature. In this manner, the fibrogenic occlusion of the blood vessel will slowly and permanently lock the coil in position at the occlusion site, while the coil is temporarily held in place by the spasm or narrowing of the vessel. This prevents or at least inhibits migration of the coil downstream through the body lumen after it has been released by the positioner.
Devices according to the present invention will generally comprise a shaft having proximal and distal ends and an axial lumen therebetween. For vascular applications, the shaft will typically be a non-conductive, tubular catheter body capable of being introduced to the vascular system over a guide wire in a conventional manner. A positioner is slidably disposed within an axial lumen of the shaft and includes a first electrode at the distal end for contacting the vaso-occlusive coil. The positioner may be a guide wire that is also used for advancing the shaft through the body lumen or a separate device inserted into the catheter body after it has been advanced to the target site. The first electrode is coupled to a source of high or radiofrequency electrical energy by the positioner itself, an electrical conductor extending through the positioner, or through the catheter body.
The positioner preferably comprises a conductive shaft having an outer insulating sheath extending to a distal portion of the shaft. The distal portion includes an engaging element for releasably engaging the vaso-occlusive coil to either deploy the coil at the target site or to reposition a deployed coil to another location in the patient""s vasculature. In one embodiment, the engaging element comprises a pair of opposed elements which can be selectively opened and closed to engage and release a proximal portion of the coil. Usually, the opposed elements will be openable jaws that are actuated manually with an actuator located on a handle at the proximal end of the positioner. In another embodiment, the distal engaging element comprises a plurality of resilient hooks that are biased away from each other and held together by the catheter body. In yet another embodiment, the distal engaging element comprises a distal pusher element adapted to contact the coil and push it through the catheter body to the target site.
The system of the present invention will also include a second electrode operatively coupled to the high frequency energy source. The second electrode can be either a second bipolar electrode disposed on the positioner (usually spaced proximally from the first electrode), the catheter. or introducing sheath, or a dispersive or return electrode attachable directly to the patient""s skin (where the first or active electrode will function in a monopolar manner). The electrodes are thus utilized to apply monopolar or bipolar high frequency energy to the vaso-occlusive coil within the vessel lumen. For example, a separate guide wire could be provided as either a monopolar or one bipolar electrode.
Frequently, the first electrode(s) will be associated with the distal engaging elements. For example, the opposing jaws or the resilient hooks can also define the treatment electrodes on the positioner. In the bipolar mode, most likely, a separate, second radiofrequency electrode can be provided on the catheter.